00:01
So in this problem, we want to look at table 10 .2 and find the molar fraction of oxygen in air, and that's 0 .21.
00:09
So this means that air is 21 % oxygen.
00:14
And so now we want to find the volume that this, that 10 grams of oxygen, the volume of air, that would be for 10 grams of oxygen.
00:26
So we can take our 10 grams of oxygen and convert it to moles by taking the molar mass of oxygen, 32 .0 grams per mole.
00:38
And we get that we have 0 .3125 moles of oxygen.
00:46
Now we want to find the moles of air that we would have from this many moles of oxygen.
00:52
So we know that oxygen, that air is 21 % oxygen, so 21 over 100, and that equals 0 .3125 moles over x, which is our unknown number of total moles.
01:11
And so here we can cross multiply...